Diagenesis

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  • Diagenesis
definition
  • The physical and chemical change undergone by sediment during lithification and compaction.  
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broader
Abstract from DBPedia
    Diagenesis (/ˌdaɪ.əˈdʒɛnəsɪs/) is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth's crust. In the early stages, the transformation of poorly consolidated sediments into sedimentary rock (lithification) is simply accompanied by a reduction in porosity and water expulsion (clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content is progressively transformed into kerogens and bitumens. The process of diagenesis excludes surface alteration (weathering) and deep metamorphism. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures. Hydrothermal solutions, meteoric groundwater, rock porosity, permeability, dissolution/precipitation reactions, and time are all influential factors. After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals (e.g., calcite, siderite, pyrite, marcasite...) during diagenesis. Porosity usually decreases during diagenesis, except in rare cases such as dissolution of minerals and dolomitization. The study of diagenesis in rocks is used to understand the geologic history they have undergone and the nature and type of fluids that have circulated through them. From a commercial standpoint, such studies aid in assessing the likelihood of finding various economically viable mineral and hydrocarbon deposits. The process of diagenesis is also important in the decomposition of bone tissue.

    続成作用(ぞくせいさよう、diagenesis)は、堆積物が固まって堆積岩になる作用。砕屑岩では主に圧密作用と膠結作用の2つからなるが、炭酸塩岩ではこれ以外の続成作用も多く見られる。

    (Source: http://dbpedia.org/resource/Diagenesis)

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